Electric cable



W. T. PEIRCE ELECTRIC CABLE Feb. 22, 1949.

Filed Jan. 15. 1946 INVENTORI M 7 5@ /Df/E,

,d-MYex/Xh HIS ATTORNEY.

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Patented Fb.422,1949

ELECTRIC CABLE Walter 'I'. leirce, Worcester, Mass., assigner to TheAmerican Steel and Wire Company of New Iersey,

l. corporation of New Jersey Application January 15, 1946, Serial No.641,204

7 Claims. 1

This invention relates to an electric cable oi the type shown in myco-pending application, Serial No. 507,693, led October 26, 1943, nowPatent No. 2,398,447, dated April 16, 1946, of which this application isa continuation-in-part. In this type of cable, the electrical`conductors and insulation are enclosed in an oil tight sheath. Due totemperature changes the pressure within the cable will vary ifcompensating means are not provided. This causes trouble due toionization and also distortion and breakage of the sheath. Variouscompensating means have been proposed, but they have not provedsatisfactory' sibility that the pressure within the cable will fallbelowatmospheric. This condition is undesirable and it is an object ofthis invention to provide an electric cable in which the pressure oi'the oil will always be above atmospheric.

Another object is to provide an electric cable having means for keepingthe'pressure throughout the length of the cable constant.

Still another object is to provide pressure compensating means which canbe easily incorporated in various types of cables having oil saturatedinsulation.

These and other objects will be more apparent afterreferring to thefollowing specification and attached drawings, in which:

Figure 1 is a cross sectional view of the cable;

Figure 2 is a schematic drawing showing one pair of tubes within thecable with joints between successive lengths of cable;

Figure 2a is a fragmentary view similar to Figure 2, but showing amodification of my invention; and

Figure 3 is a view similar to Figure 1, but showing a modification of myinvention.

Referring more particularly to the drawings,

i the reference numeral 2 indicates the metallic conductors of thecable, each of which is surrounded by oil impregnated insulation 4. Ametallic tape 8 surrounds the insulation l and a metallic and fibrousbinder 8 holds the three conductors 2 together and makes contact between.the conductors 2 are a plurality of concentric tubes I2 and I l. Thespace in the interstices between the conductors not occupied by theconcentric tubes I2 and Il is filled with fibrous material I6.

Figure 2 is a schematic representation drawn out of scale to illustratethe operation of the system when several lengths of cable constructed asin Figure 1 are joined together. The conductors and insulation areomitted from'the drawing for the sake of simplicity. The outer tube I2is provided with openings I8 at spaced apart intervals for a purposewhich will appear later. The lengths of cable are spliced together atthe enlarged section 20. Within this enlarged section 20 Iis a manifold22 which joins the ends of the two adjacent sections of the outer tubeI2. The ends of the inner tubes I4 are open to the manifold 22. Insteadof using a separate manifold 22, the contiguous outer tubes ILof eachlength of cable may be spliced together by means of a splicing sleeve 23and the inner tubes Il broken at the splice as shown in Figure 2a sothat the gas therein will have access to the space between the tubes. Inother words the splice acts as the manifold.

In the manufacture of the cables, the inner tube I4 is iirst extrudedfrom copper or other flexible material and the outer tube I2 is thenextruded from similar material around the outside of tube I4 andperforated at intervals. The conductors l2 are covered with theinsulation l which may be helically applied paper tape. The threeconductors 2 and the three pairs of tubes I2, Il are put on separatecradles and cabled together in the usual manner by rotating the cradlesas the cabled conductors are advanced. The assembly is then placed in atank and the inner tube Il is flushed out with an inert gas such asnitrogen and sealed ofi'. Heat and vacuum are applied to the cable toremove all gas and moisture and the tank is illled with an insulatingoil to impregnate the insulation 4. This oil will enter the openingslIII and ll completely the space between the tubes I2 and Il, as well asall other voids within the cable structure. The protective sheath I0,which is generally made of lead, is then extruded over the cable. Thecable is made up in lengths convenient to handle, such as 500 feet, andseveral such lengths are fastened together to provide the total lengthrequired. At each joint 20 the outer tubes I2 are connected to thecommon manifold The sealsffare removed from the ends of the inner tubesiu which are then open to the manifold z2.

When the cable changes in temperature due to atmospheric changes orheating, the components of'the cable expand. The pressure developedcausesgthe liquid with which the cable was impregnated to enter theopenings IB and iiow along the space'between the tubes I2 and I4 towardmanifold 22 which will ll with oil coming from both directions and nallyenter the open ends of tubes i4. Since tube i4 is small, the oil willblock the cross section of the tube due to the wetting tension betweenit and the wall of the tube and prevent the gas from escaping.Additional oil will gradually compress the gas originally in tube Ilbetween the oil blocks entering both ends. Thus the gas in the tube Ilwill act as a cushion to provide space in the cable structure to takecare of the expanding liquid without undue pressureA change.` When thecable cools oil?, the compressed gas in tube I4 will force the liquidback to the manifold'22, through the space between tubes I2 and I4,andthrough the openings I8 back into the cable'structure.

Figure 3 shows a pair of tubes 24 and 26 which description of Figure 2is equally applicable to this' second embodiment if reference numerals24 and 26 are substituted for reference numerals i2 and i4. Thedescription of the operation of the pressure compensating means forFigures 1 and 2 is equally applicable to this embodiment.

While two embodiments of my invention have been shown and described, itwill be apparent that other adaptations and modifications may be madewithout departing from the scope of the following claims.

I claim: "1

i. A cable comprising a conductor. insulation about the conductorincluding a liquid, a duidtight sheath about the insulation, a tubecontaining gas disposed within said sheath, an outer tube surroundingand substantially parallel to the rst tube and providing a spacetherebetween, said outer tube having an opening therein for admittingliquid thereto, and a manifold, said outer tube terminating in saidmanifold, said inner tube opening intosaid manifold whereby the liquidupon expansion will venter into said inner tube and compress thegas-therein.

2. A cable comprising a conductor, insulation about the conductorincluding a liquid, a fluidtight'sheath about the insulation, a. tubecontaining gas disposed within said sheath, an outer tube surroundingand substantially parallel to the first tube and providing a spacetherebetween, said outer tube having openings therein at spacedintervals for admitting liquid thereto, and a manifold at each end ofthe outer tube, said inner tube opening into said manifold whereby theliquid upon expansion will enter into said inner tube and compress thegas therein.-

3. A cable comprising a conductor, insulation about the conductorincluding a liquid, a fluidtight sheath about the insulation, aplurality oi tubes containing gas disposed within said sheath, an outertube surrounding each of said tubes and substantially parallel theretoand providing a space therebetween, said outer tubes having openingstherein at spaced intervals for admitting liquid thereto, and a manifoldat each end of the outer tubes, said inner tubes opening into saidmanifold whereby the liquid upon expansion will enter into said innertubes and compress the gas therein.

A cable comprising a conductor, insulation about the conductor includinga liquid, a fluidtight sheath about the insulation, a tube containinggas disposed within said sheath, a second tube adjacent said rst' tube,said second tube having an opening therein for `admitting liquidthereto, and amanifold, said second tube terminating in said manifold,said first tube opening into said manifold whereby the liquid uponexpansion will enter into said first tube and compress the gas therein.

5. A cable comprising a conductor, insulation about the conductorincluding a liquid, a uidtight sheath about the insulation, a tubecontaining gas disposed within said sheath, a second tube adjacent saidfirst tube, said second tube having openings therein at spaced intervalsfor admitting liquid thereto, and a manifold at each end of the secondtube, the rst tube opening into said manifold whereby the liquid uponexpansion will enter into said first tube and compress the gas therein.

6. A cable comprising `a conductor, insulation about the conductorincluding a liquid, a fluidtight sheath about the insulation, aplurality of tubes containing gas disposed within said sheath, a tubeadjacenteach of said first named tubes, each of said last named tubeshaving openings therein at spaced intervals for admitting liquidthereto, and a manifold at each 'end of the last named tubes, the rsttubes opening into said manifold whereby the liquid upon expansion willenter into said nrst tubes and compress the gas therein.

7. A system for the transmission of electrical energy comprising atleast two lengths of cable spliced together, each of such lengths ofcable comprising a conductor, insulation about the conductor including aliquid, a iluid tight sheath about the insulation, a tube containing gasdisposed within said sheath, an outer tube surrounding and substantiallyparallel to the rst tube and providing a space therebetween, said outertube having an opening therein for admitting liquid thereto, and asplice between the contiguous outer tubes of each length of cable, theinner tube being broken at said splice so that the gas therein hasaccess to the space between the tubes at the splice.

WALTER T. PE.

REFERENCES CITED ille of this patent:

UNITED STATES PATENTS Name 'Date Peirce Apr. 16, 1946 Number

